BRUSSELS -- NATO Secretary-General Jens Stoltenberg says the Western alliance is assessing whether Russia has pulled out all the troops it sent to Belarus for joint exercises last month that were watched warily by neighbors.

Speaking in an interview in Brussels on October 5, Stoltenberg told RFE/RL that NATO "closely monitored the Zapad exercise" but that "it is too early to make any final assessment" on the drill.

"The important thing is that any troops can only stay in Belarus with the consent of the government in Belarus, and the Russian minister of defense has announced that they have withdrawn all the troops," he said, adding: "We are now assessing this.”

The September 14-20 war games in Belarus and parts of western Russia triggered concerns in neighboring NATO nations already wary of Moscow's intentions after its annexation of Ukraine’s Crimean Peninsula in March 2014 and military interference in eastern Ukraine.

Moscow and Minsk said the maneuvers involved some 12,700 troops in the two countries combined, but Western officials have said the true number may have been around 100,000.

On September 30, Moscow denied a claim made by the Ukrainian military chief of staff, Viktor Muzhenko, that Russia left troops in Belarus after the drills.

The Belarusian Defense Ministry had said that the last train of Russian troops who participated in the Zapad 2017 military drills left Belarus on September 28.

Stoltenberg told RFE/RL that the Western military alliance currently doesn’t see “any imminent threat against any NATO ally,” but he added that what “we see is a more assertive Russia, a Russia which has implemented a significant military buildup over many years, increased defense spending, more modern capabilities, exercises of its forces, and a Russia that has been willing to use military force against its neighbors, especially in Ukraine.”

The NATO chief also admitted that the relationship between NATO and Moscow has “deteriorated over the last years, especially since the illegal annexation of Crimea and Russia's continued efforts to destabilize eastern Ukraine and its support to the separatists there.”

Despite the tensions, NATO has kept dialogue with Russia open via the NATO-Russia Council, which last met in Brussels in July. Although few concrete outcomes have been achieved following several rounds of talks, envoys of Russia and NATO are poised to meet again in the autumn.

“Russia is there to stay, NATO doesn't want a Cold War, we don't want a new arms race. Therefore, we also reach out to Russia for political dialogue,” Stoltenberg said.

Speaking about a Russian proposal to send United Nations peacekeepers to eastern Ukraine, Stoltenberg said the troops should patrol the whole conflict zone including the border between Russia and the separatist-held parts of Ukraine's Donetsk and Luhansk regions, which Kyiv says is used to ship weapons and military personnel in from Russia.

“We welcome all ideas and proposals that can help us implement the Minsk agreement, meaning respect the cease-fire, withdrawal of heavy weapons,” he said.

The war between Russia-backed separatists and Ukrainian government forces has killed more than 10,000 people in eastern Ukraine since April 2014.

The conflict has persisted despite an agreement signed in Minsk in February 2015 and a September 2014 deal that was also signed in the Belarusian capital that called for a cease-fire and set out steps to end the conflict that have gone largely unimplemented.

Sanctions imposed by the European Union, the United States, and other countries have not prompted Russia to abandon its support for the separatists or fulfill its commitments under the Minsk agreements.